The present invention relates to a device for tensioning at least two essentially length-invariant belts, whereby a first belt is guided around a first axis, which repeatedly performs an adjustment movement in an adjustment direction that runs orthogonally to the axial direction of the first axis, and whereby the first belt and a second belt are guided about a common second axis, whereby the tensioning directions of the first belt and of the second belt, in the region of the second axis, form a varying angle of between 0° and 180°.
In connection with the present invention, when the teaching “essentially length-invariant belts” is used, what is meant is that the belts practically cannot be reacted by means of a change in length from an outer force acting on them, as is the case, for example, with common polyurethane belts. Of course, it is clear, however, that this type of length-invariant, or rigid material, has a known elasticity. This insignificant elasticity, however, does not contradict the fact that in the frame of the present invention, the belts are essentially length-invariant.
In addition, when the teaching is that a belt is “guided around an axis”, it should also be understand that the belt is guided about a belt pulley, or a pinion, which is rotatably attached on a rigid axis, or rigidly attached on a rotatably shaft. It is also contemplated, however, that the belt is guided about a plurality of correlated axes, for example, based on common movement.
Finally, regarding the tensioning directions of the first and second belts, it is to be understood that what is meant is the positive direction of the respective tensioning forces which these belts exert on the second axis.
These types of lifting-transverse units, as are disclosed, for example, in DE 30 12 355 A1 and DE 196 03 554 A1, serve in a conveyance system for work pieces, or work piece carriers, to stop work pieces, or work piece carriers, transported on a first conveying track, to lift the work pieces or work piece carriers from the conveyor means of the first conveyor track, and to transfer the work pieces or work piece carriers to a second conveyor track that is mostly orthogonal to the first conveyor track. The lifting-transverse unit includes a lifting unit with integrated lift apparatus, for example, a pneumatic cylinder, and one or more guide rods. With a positioning element of the force apparatus, for example, the piston rod of the pneumatic cylinder, and the guide rods, a lifting plate is rigidly connected, on which a plurality of axes for supporting guide pulleys for tensioning belts are provided. These axes together form “a first axis” in the sense of the present invention. By means of the tensioning belts, the work piece, or the work piece carrier, is transported after lifting from the first conveyor track to the second conveyor track. For driving the tensioning belts, these are guided about a further axis, about which also a drive belt is guided, which, in turn, is driven by a geared motor or the like.
With the lifting-transverse unit HQ2/S, also the lifting movement is made with the common axis of the tensioning belts and drive belts, so that as a result, this lifting movement indeed does not change the tensioning or stretching of the tensioning belts, rather the tensioning of the drive belts. Therefore, a tensioning device in the form of tension rollers are provided, which, upon the assembly of the entire device, are adjusted. The change in length on the belts is therefore not equalized; that is, the tensioning is different depending on the stroke adjustment. Upon use of an addition, spring-loaded tension roller, the belt tension can be held constant.
In addition, a further lifting-transverse unit of Bosch GmbH is known, namely, the lifting-transverse unit HQ1/O. With this unit, the drive belt is formed from a loop of polyurethane so that it can reacted to the lifting movement as well as the manufacturing and assembly tolerances by means of an elastic elongation or extension, that is, by means of a change in length.